1.\" Copyright (c) 1983, 1990, 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. All advertising materials mentioning features or use of this software 13.\" must display the following acknowledgement: 14.\" This product includes software developed by the University of 15.\" California, Berkeley and its contributors. 16.\" 4. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" From: @(#)inet.3 8.1 (Berkeley) 6/4/93 33.\" $FreeBSD$ 34.\" 35.Dd June 17, 1996 36.Dt INET 3 37.Os 38.Sh NAME 39.Nm inet_aton , 40.Nm inet_addr , 41.Nm inet_network , 42.Nm inet_ntoa , 43.Nm inet_ntop , 44.Nm inet_pton , 45.Nm inet_makeaddr , 46.Nm inet_lnaof , 47.Nm inet_netof 48.Nd Internet address manipulation routines 49.Sh LIBRARY 50.Lb libc 51.Sh SYNOPSIS 52.In sys/types.h 53.In sys/socket.h 54.In netinet/in.h 55.In arpa/inet.h 56.Ft int 57.Fn inet_aton "const char *cp" "struct in_addr *pin" 58.Ft in_addr_t 59.Fn inet_addr "const char *cp" 60.Ft in_addr_t 61.Fn inet_network "const char *cp" 62.Ft char * 63.Fn inet_ntoa "struct in_addr in" 64.Ft const char * 65.Fo inet_ntop 66.Fa "int af" 67.Fa "const void * restrict src" 68.Fa "char * restrict dst" 69.Fa "socklen_t size" 70.Fc 71.Ft int 72.Fn inet_pton "int af" "const char * restrict src" "void * restrict dst" 73.Ft struct in_addr 74.Fn inet_makeaddr "in_addr_t net" "in_addr_t lna" 75.Ft in_addr_t 76.Fn inet_lnaof "struct in_addr in" 77.Ft in_addr_t 78.Fn inet_netof "struct in_addr in" 79.Sh DESCRIPTION 80The routines 81.Fn inet_aton , 82.Fn inet_addr 83and 84.Fn inet_network 85interpret character strings representing 86numbers expressed in the Internet standard 87.Ql .\& 88notation. 89.Pp 90The 91.Fn inet_pton 92function converts a presentation format address (that is, printable form 93as held in a character string) to network format (usually a 94.Ft struct in_addr 95or some other internal binary representation, in network byte order). 96It returns 1 if the address was valid for the specified address family, or 970 if the address wasn't parseable in the specified address family, or -1 98if some system error occurred (in which case 99.Va errno 100will have been set). 101This function is presently valid for 102.Dv AF_INET 103and 104.Dv AF_INET6 . 105.Pp 106The 107.Fn inet_aton 108routine interprets the specified character string as an Internet address, 109placing the address into the structure provided. 110It returns 1 if the string was successfully interpreted, 111or 0 if the string is invalid. 112The 113.Fn inet_addr 114and 115.Fn inet_network 116functions return numbers suitable for use 117as Internet addresses and Internet network 118numbers, respectively. 119.Pp 120The function 121.Fn inet_ntop 122converts an address from network format (usually a 123.Ft struct in_addr 124or some other binary form, in network byte order) to presentation format 125(suitable for external display purposes). 126It returns NULL if a system error occurs (in which case, 127.Va errno 128will have been set), or it returns a pointer to the destination string. 129This function is presently valid for 130.Dv AF_INET 131and 132.Dv AF_INET6 . 133.Pp 134The routine 135.Fn inet_ntoa 136takes an Internet address and returns an 137.Tn ASCII 138string representing the address in 139.Ql .\& 140notation. The routine 141.Fn inet_makeaddr 142takes an Internet network number and a local 143network address and constructs an Internet address 144from it. The routines 145.Fn inet_netof 146and 147.Fn inet_lnaof 148break apart Internet host addresses, returning 149the network number and local network address part, 150respectively. 151.Pp 152All Internet addresses are returned in network 153order (bytes ordered from left to right). 154All network numbers and local address parts are 155returned as machine byte order integer values. 156.Sh INTERNET ADDRESSES 157Values specified using the 158.Ql .\& 159notation take one 160of the following forms: 161.Bd -literal -offset indent 162a.b.c.d 163a.b.c 164a.b 165a 166.Ed 167.Pp 168When four parts are specified, each is interpreted 169as a byte of data and assigned, from left to right, 170to the four bytes of an Internet address. Note 171that when an Internet address is viewed as a 32-bit 172integer quantity on the 173.Tn VAX 174the bytes referred to 175above appear as 176.Dq Li d.c.b.a . 177That is, 178.Tn VAX 179bytes are 180ordered from right to left. 181.Pp 182When a three part address is specified, the last 183part is interpreted as a 16-bit quantity and placed 184in the right-most two bytes of the network address. 185This makes the three part address format convenient 186for specifying Class B network addresses as 187.Dq Li 128.net.host . 188.Pp 189When a two part address is supplied, the last part 190is interpreted as a 24-bit quantity and placed in 191the right most three bytes of the network address. 192This makes the two part address format convenient 193for specifying Class A network addresses as 194.Dq Li net.host . 195.Pp 196When only one part is given, the value is stored 197directly in the network address without any byte 198rearrangement. 199.Pp 200All numbers supplied as 201.Dq parts 202in a 203.Ql .\& 204notation 205may be decimal, octal, or hexadecimal, as specified 206in the C language (i.e., a leading 0x or 0X implies 207hexadecimal; otherwise, a leading 0 implies octal; 208otherwise, the number is interpreted as decimal). 209.Pp 210The 211.Fn inet_aton 212and 213.Fn inet_ntoa 214functions are semi-deprecated in favor of the 215.Xr addr2ascii 3 216family. However, since those functions are not yet widely implemented, 217portable programs cannot rely on their presence and will continue 218to use the 219.Xr inet 3 220functions for some time. 221.Sh DIAGNOSTICS 222The constant 223.Dv INADDR_NONE 224is returned by 225.Fn inet_addr 226and 227.Fn inet_network 228for malformed requests. 229.Sh SEE ALSO 230.Xr addr2ascii 3 , 231.Xr byteorder 3 , 232.Xr gethostbyname 3 , 233.Xr getnetent 3 , 234.Xr inet_net 3 , 235.Xr hosts 5 , 236.Xr networks 5 237.Rs 238.%R RFC 239.%N 2373 240.%D July 1998 241.%T "IP Version 6 Addressing Architecture" 242.Re 243.Sh STANDARDS 244The 245.Fn inet_ntop 246and 247.Fn inet_pton 248functions conform to 249.St -xns5.2 . 250Note that 251.Fn inet_pton 252does not accept 1-, 2-, or 3-part dotted addresses; all four parts 253must be specified and are interpreted only as decimal values. 254This is a narrower input set than that accepted by 255.Fn inet_aton . 256.Sh HISTORY 257These 258functions appeared in 259.Bx 4.2 . 260.Sh BUGS 261The value 262.Dv INADDR_NONE 263(0xffffffff) is a valid broadcast address, but 264.Fn inet_addr 265cannot return that value without indicating failure. 266The newer 267.Fn inet_aton 268function does not share this problem. 269The problem of host byte ordering versus network byte ordering is 270confusing. 271The string returned by 272.Fn inet_ntoa 273resides in a static memory area. 274.Pp 275Inet_addr should return a 276.Fa struct in_addr . 277